Cleanup: tests: Branch condition evaluates to a garbage value

[urcu.git] / urcu-bp.c

diff --git a/urcu-bp.c b/urcu-bp.c
index 4dc402865a026800ccef0bb35378be6241c81505..20684cc4d0972a61427f8ecae0e5fd7eb5072189 100644 (file)
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -36,6 +36,7 @@
 #include <unistd.h>
 #include <sys/mman.h>
 
+#include "urcu/arch.h"
 #include "urcu/wfcqueue.h"
 #include "urcu/map/urcu-bp.h"
 #include "urcu/static/urcu-bp.h"
@@ -94,11 +95,25 @@ void *mremap_wrapper(void *old_address, size_t old_size,
 static
 int rcu_bp_refcount;
 
+/* If the headers do not support membarrier system call, fall back smp_mb. */
+#ifdef __NR_membarrier
+# define membarrier(...)               syscall(__NR_membarrier, __VA_ARGS__)
+#else
+# define membarrier(...)               -ENOSYS
+#endif
+
+enum membarrier_cmd {
+       MEMBARRIER_CMD_QUERY = 0,
+       MEMBARRIER_CMD_SHARED = (1 << 0),
+};
+
 static
 void __attribute__((constructor)) rcu_bp_init(void);
 static
 void __attribute__((destructor)) rcu_bp_exit(void);
 
+int urcu_bp_has_sys_membarrier;
+
 /*
  * rcu_gp_lock ensures mutual exclusion between threads calling
  * synchronize_rcu().
@@ -174,6 +189,14 @@ static void mutex_unlock(pthread_mutex_t *mutex)
                urcu_die(ret);
 }
 
+static void smp_mb_master(void)
+{
+       if (caa_likely(urcu_bp_has_sys_membarrier))
+               (void) membarrier(MEMBARRIER_CMD_SHARED, 0);
+       else
+               cmm_smp_mb();
+}
+
 /*
  * Always called with rcu_registry lock held. Releases this lock between
  * iterations and grabs it again. Holds the lock when it returns.
@@ -254,7 +277,7 @@ void synchronize_rcu(void)
        /* All threads should read qparity before accessing data structure
         * where new ptr points to. */
        /* Write new ptr before changing the qparity */
-       cmm_smp_mb();
+       smp_mb_master();
 
        /*
         * Wait for readers to observe original parity or be quiescent.
@@ -303,7 +326,7 @@ void synchronize_rcu(void)
         * Finish waiting for reader threads before letting the old ptr being
         * freed.
         */
-       cmm_smp_mb();
+       smp_mb_master();
 out:
        mutex_unlock(&rcu_registry_lock);
        mutex_unlock(&rcu_gp_lock);
@@ -567,6 +590,10 @@ void rcu_bp_init(void)
                                urcu_bp_thread_exit_notifier);
                if (ret)
                        abort();
+               ret = membarrier(MEMBARRIER_CMD_QUERY, 0);
+               if (ret >= 0 && (ret & MEMBARRIER_CMD_SHARED)) {
+                       urcu_bp_has_sys_membarrier = 1;
+               }
                initialized = 1;
        }
        mutex_unlock(&init_lock);